1. Field of the Invention
The subject invention relates to sheet handling and stacking and, more specifically, to methods and apparatus for handling or for stacking sheets, such as bank checks, invoices, data and other cards, documents, copying or duplicating machine sheets and the like.
2. Description of Prior Art
In the broad context of data processing, the efficiency and feasibility of automated bank check and invoice processing have been lagging for lack of suitable equipment. In particular, prior-art sheet handling and sheet stacking methods have constituted a bottleneck in the development of sheet handling and sheet stacking techniques and equipment that would keep pace with other processing aspects concerning handled or stacked bank checks and invoices.
Similar observations apply to the processing, handling and stacking of punched and other data cards, to the processing, handling and stacking of documents, to the handling and stacking of sheets in copy machines or duplicators, and in general to other areas where sheets or sheet-like objects are handled or stacked.
In this respect, a prior-art document feeding mechanism is apparent from U.S. Pat. No. 3,095,192, by L. P. Simjian, issued June 25, 1963, and employing a plate coupled to a document feeding roller for cyclically rocking motion to permit the feeding of documents into a depository and to thereafter maintain each fed document substantially flat in the depository. This prior-art mechanism assumes the feeding progress of each document from the operation of the particular feed roller, rather than operating on the basis of the document progress itself.
According to U.S. Pat. No. 3,061,304, by J. G. Smith, issued Oct. 30, 1962, feeler fingers, depending downwardly by force of gravity, are employed in a sheet magazine to guide leading edges of ejected sheets downwardly to their stacked position in the magazine, to keep sheets stacked in the magazine, and to indicate when the magazine has been filled with stacked cards. A similar proposal is apparent from U.S. Pat. No. 3,847,391, by William Brant et al, issued Nov. 12, 1974. In both of these proposals, the role of the employed hold-down fingers in the stacking process is necessarily limited by the fact that the sheets advancing into the stacker must be capable of lifting and sliding under the fingers, which imposes expensive limitations on the permissible weight and force of application of the fingers on the stack.
A different kind of proposal is apparent from U.S. Pat. No. 3,847,388, by Thomas Lynch, issued Nov. 12, 1974, wherein a series of flexible flappers is drawn into the feed roller nip at the entrance of a tray and is thereupon flailed down on the sheets in the tray for driving fed sheets downwardly into the stack.
In practice, such flailing elements tend to wear faster than the remainder of the mechanism and their utility is limited by the permissible extent of their action on the sheets without deformation or damage thereof.
A more advantageous proposal has a slidable magazine and uses a plunger or thumper for incrementally actuating the slidable magazine as sheets are fed thereinto. While this proposal advantageously increases the volume of the magazines to accommodate a growing stack of sheets, the thumper actuation is burdened by the drawbacks of prior-art sheet feeding mechanisms. In this respect, reference may, for instance, be had to U.S. Pat. No. 3,672,265, by August Schwarzkopf, issued June 27, 1972, and showing photocell sensors with cooperating electrical or pneumatic motors in the context of stacking apparatus.
The failure of the prior art to develop adaptable solutions for present purposes may, for instance, be seen from U.S. Pat. Nos. 1,887,023, 2,013,153, 2,991,999, 3,739,925, 3,805,971, and 2,916,286.